摘要:

ABSTRACTChickpeas were grown with or without nitrate nitrogen feeding, or nodulated withRhizobium leguminosarum.High [40°C day, 25°C night (HT)] and moderate [25°C day, 177°C night (LT)]temperature regimes were employed during growth. Growth rates, photosynthetic capacity and enzymes of carbon and nitrogen metabolism were monitored to assess the acclimatory capacity of the chickpea. Initial growth rates were stimulated by high temperatures, particularly in nitrate‐fed and nodulated plants. Older HT plants had fewer laterals, smaller leaves, and fewer flowers were produced than in LT plants. There was some indication of an acclimation of photosynthesis to high temperatures and this was independent of nitrogen supply. Rubisco activity was increased by high growth temperatures. However, HT plants also had higher transpiration rates and lower water use efficiency than LT plants both in respective growth conditions and when compared in a common condition. High temperatures reduced shoot nitrate reductase activity but had little effect on root activity, which was the same if not greater than activity in LT roots. The amino acid, asparagine, was found at high concentrations in all treatments. Concentrations were maintained throughout growth in HT plants but declined with age in LT p

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1993.tb00479.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

ABSTRACTPhotosynthetic gas exchange and the stable isotopic composition of foliage water were measured for a xylem tapping mistletoe,Phoradendron juniperinum, and its host tree,Juniperus osteosperma, growing in southern Utah. The observed isotopic composition of water extracted from foliage was compared to predictions of the Craig‐Gordon model of isotopic enrichment at evaporative sites within leaves. Assimilation rates of juniper were higher and stomatal conductance was lower than the values observed for the mistletoe. This resulted in lower intercellular/ ambient CO2values in the juniper tree relative to its mistletoe parasite. For mistletoe, the observed foliage water hydrogen and oxygen isotopic enrichment was less than that predicted by the model. In juniper, foliage water hydrogen isotopic enrichment was also lower than that predicted by the evaporative enrichment model. In contrast, the oxygen isotopic enrichment in juniper foliage water was slightly greater than that predicted for the evaporative sites within leaves. Hydrogen isotopic enrichment in mistletoe foliage shows systematic variation with stem segment, being highest near the tips of the youngest stems and decreasing toward the base of the mistletoe, where isotopic composition is close to that of stem water in the host tree. In a correlated pattern, mid‐day stomatal conductance declined abruptly in mistletoe foliage of increasing

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1993.tb00480.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

ABSTRACTThe extracellular electrical potential inBidens pilosahas been compared with the transmembrane potential in hypocotyl cells. We found that variations in the extracellular electrical potential, induced by different KCI concentrations, were identical to the variations of the transmembrane potential. In order to explain the strong correlation between the extracellular potential and the transmembrane potential, an interpretative model based on the electrical diagram of the plant was tested. From our data, we found that: (1) the symplast behaves as a low resistance pathway compared with the apoplast; and (2) the cell wall contributes weakly (20% at the most) to the transmembrane potential. It is concluded that each hypocotyl cell is strongly coupled electrically with its neighbour. This property, together with the high apoplast resistance, accounts for the similarity in the extracellular and transmembrane potential measurements. These properties, which are characteristic of excitable organs, support the existence of action potentials inBidens.

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1993.tb00481.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

ABSTRACTLeaves ofTriticum aestivumcv. Avalon were grown in an atmosphere that contained 150 nmole mol‐1ozone for 7h each day. After leaves had reached maximum size, the leaf blade was divided into three sections to provide tissue of different age, the youngest at the base of the blade and the oldest at the leaf tip. The ozone treatment was found to decrease significantly the light‐saturated rate and quantum yield of CO2assimilation and the maximum quantum yield of photosystem II photochemistry in the oldest leaf section. No effects were found on the basal and middle sections of the leaf. These ozone‐induced decreases in the photosynthetic parameters were associated with decreases in the efficiency of utilization of light for CO2assimilation at the photon flux density under which the leaves were grown. The depression in photosynthetic performance of tissue near the leaf tip was accompanied by large decreases in the contents of total, soluble and thylakoid proteins and chlorophyll. There was also found to be a preferential loss of ribulose‐1,5‐carboxylase‐oxygenase. These ozone‐induced changes in chlorophyll and protein contents and the photosynthetic activities of the leaf tissue were similar to changes normally associated with leaf senescence. Two‐dimensional polyacrylamide gel analyses of leaf proteins demonstrated the loss of some minor, and unidentified, proteins, whilst another group of minor proteins appeared. It is concluded that daily exposure of the leaf to 150 nmol mol‐1ozone for 7h had no effect on the development of the photosynthetic apparatus and its activities during leaf expansion, but it did promote the onset of premature senescence in fully expanded tissue that resulted in a loss of pigments, proteins and photosynthetic capaci

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1993.tb00482.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

ABSTRACTCarbon transport across the plasma membrane, and carbon fixation were measured in perfusedCharainternodal cells. These parameters were measured in external media of pH 5·5 and pH 8·5, where CO2and HCO3‐are, respectively, the predominant carbon species in both light and dark conditions. Cells perfused with medium containing ATP could utilize both CO2and HCO3‐from the external medium in the light. Photosynthetic carbon fixation activity was always higher at pH 5·5 than at pH 8·5. When cells were perfused either with medium containing hexokinase and 2‐deoxyglucose to deplete ATP from the cytosol (HK medium) or with medium containing vanadate, a specific inhibitor of the plasma membrane H+‐ATPase (V medium), photosynthetic carbon fixation was strongly inhibited at both pH 5·5 and 8·5. Perfusion of cells with medium containing pyruvate kinase and phosphoenolpyruvate (PEP) to maximally activate the H+‐ATPase (PK medium), stimulated the photosynthetic carbon fixation activities. Oxygen evolution of isolated chloroplasts and the carbon fixation of cells supplied14C intracellularly were not inhibited by perfusion media containing either hexokinase and 2‐deoxyglucose or vanadate. The results indicate thatCharacells possess CO2and HCO3‐transport systems energized by ATP and sensitive to vanadate in the light. In the dark, intact cells also fix carbon. By contrast, in cells perfused with medium containing ATP, no carbon fixation was detected in 1 mol m‐3total dissolved inorganic carbon (TDIC) at pH 8·5. By increasing TDIC to 10 mol m‐3, dark fixation became detectable, although it was still lower than that of intact cells at 1mol m‐3TDIC. Addition of PEP or PEP and PEP carboxylase to the perfusion media significantly increased the dark‐carbon fixation. Perfusion with vanadate had no effect

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1993.tb00483.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

ABSTRACTThe influence of flooding with tap water, and with 10 and 20% sea water on the growth, yield and physiological characteristics in hexaploid triticale (XTriticosecaleWittmack) were analysed. The plants were grown in a glasshouse and flooded at the booting stage for 19 d. Flooding seriously affected the growth, yield and physiological activities of the plants. However, the growth and yield were greater in plants flooded with diluted sea water than in plants flooded with tap water. The amount of newly developed roots, photosynthetic rate and accumulation of mineral nutrients in the leaves was greater in sea water‐flooded plants as compared to tap water‐flooded plants. Oxygen concentrations in the diluted sea water were lower than in the tap water 6 d from the beginning of flooding. Leaf water potentials in the plants flooded with diluted sea water were lower than in the plants flooded with tap water until 7 d from the beginning of flooding when the position reversed. Transpiration was slower and stomatal resistance was greater in flooded plants, and were similar irrespective of water qual

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1993.tb00484.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

ABSTRACTThe reversible dissipation of excitation energy in higher plants is believed to protect against light‐induced damage to the photosynthetic apparatus. This dissipation is measured as the non‐photochemical quenching of chlorophyll fluorescence. A method is described whereby the saturated capacity for rapidly reversible non‐photochemical quenching can be compared between plant species. This method was applied to 22 common British plant species whose habitat was quantified using an index that describes shade tolerance. An association was found between occurrence in open habitats and a high capacity for non‐photochemical quenching. It was found that, whilst this capacity was species dependent, it did not depend upon the conditions under which the plant was grown. The possible role of zeaxanthin as a determinant of quenching capacity was examined by measuring the contents of xanthophyll cycle carotenoids for each species. Comparing species, no correlation was seen between the saturated level of non‐photochemical quenching and zeaxanthin content expressed relative to either total carotenoid or to chlorophyll. When zeaxanthin was expressed relative to the amount of xanthophyll cycle intermediates (zeaxanthin, antheraxanthin and violaxanthin), a weak correlation

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1993.tb00485.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

ABSTRACTThe pigment composition of leaves from a number of different plant species collected from field sites in the region of Sheffield, UK, have been compared using high‐performance liquid chromatography. Expression of pigment content per unit leaf area was dominated by variation in the total leaf chlorophyll. Neither chlorophyll per unit area nor the chlorophylla/bratio were found to be correlated with the habitat from which the plants originated. When the amounts of different carotenoids were expressed relative to the total carotenoid pool, it was found that whilst neither total carotene (α‐ +β‐carotene) nor neoxanthin correlated with ability to grow in shade, the leaf content of both lutein and the total xanthophyll cycle carotenoids (zeaxanthin, anther‐axanthin and violaxanthin) did, with lutein content being high in shade species and xanthophyll cycle intermediates low. There was a strong negative correlation between the relative amounts of each of these groups of carotenoids. The ratio of lutein to xanthophyll cycle carotenoids was strongly correlated to an index of shade

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1993.tb00486.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

ABSTRACTIn two experiments, winter wheat (Triticum aestivumcv. Cerco) was grown in 350 (ambient) and 700 μmol mol‐1(elevated) atmospheric CO2concentrations. In the first experiment, plants were grown at five levels of nitrogen fertilization, and in the second experiment, plants were grown at three levels of water supply. All plants were infected with powdery mildew, caused by the fungusErysiphe graminis.Plants grown in elevated atmospheric CO2concentrations had significantly reduced % shoot nitrogen contents and significantly increased % shoot water contents. At elevated atmospheric CO2concentrations, where plant nitrogen content was significantly reduced, the severity of mildew infection was significantly reduced, and where host water content was significantly increased, the severity of mildew infection was significantly increased. In a moderate water supply treatment, the plants grown in elevated atmospheric CO2concentrations had significantly reduced nitrogen contents (9·9%) and significantly increased water content (4%), the amount of mildew infection was unchanged. The severity of mildew infection appeared to be more sensitive to host water content than to host nitrogen cont

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1993.tb00487.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

ABSTRACTAlfalfa is sensitive to waterlogging, and its yields are significantly reduced under this condition. We investigated the effects of soil flooding on free abscisic acid (ABA) accumulation in shoots and roots of alfalfa in relation to plant growth and stomatal conductance responses. The production of dry matter in alfalfa was significantly affected by flooding mainly as a result of a rapid reduction in root growth. Shoot dry matter accumulation was maintained during the first 10 d of treatment and started to decline thereafter. Foliar concentration of the major mineral elements (N, P, K) was reduced by flooding, whereas only K concentration decreased in roots of flooded plants. Regrowth declined with duration of flooding and was less than 50% of controls after 2 weeks. While no changes in ABA concentration could be detected in flooded roots, an increase was noted within a few days in leaves when compared to unflooded controls. This increase in free ABA coincided with the accumulation of large quantities of starch in leaves and a rapid decline in leaf stomatal conductance. Our results support the suggestion that leaf ABA originates from the leaf itself and may be accumulating along with starch as a result of reduced translocation to the roots. Our observation of large accumulations of sucrose in flooded roots agrees with previous reports that supply of carbohydrates is not a limiting factor to root anaerobic metabolism in flooded alfalfa.

ISSN:0140-7791    

DOI:10.1111/j.1365-3040.1993.tb00488.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY